In persons with tibiotalar osteoarthritis (OA), subtalar joint motion during the stance phase of gait in the sagittal, coronal, and transverse rotational planes tends to occur in a direction opposite to that in persons who have normal ankles, according to researchers in the department of orthopedic surgery at Massachusetts General Hospital in Boston. This phenomenon represents a breakdown in the normal motion coupling seen in healthy ankle joints.

Kozanek and associates¹ used MRI and dual fluoroscopic imaging techniques to measure kinematics of the ankle joint complex in 6 patients with unilateral post-traumatic tibiotalar OA in simulated weight-bearing positions and compared the data with those from a normal cohort in a previous study. From heel strike to midstance, the tibiotalar joint with OA demonstrated 2.2° ± 5.0° of dorsiflexion and the healthy joint plantar flexed 9.1° ± 5.3°. From midstance to toe off, the subtalar joint with OA dorsiflexed 3.3° ± 4.1° and the healthy joint plantar flexed 8.5° ± 2.9°. The subtalar joint in the group with OA rotated externally 1.2° ± 1.0° and everted 3.3° ± 6.1° from midstance to toe off; in the joint in the control group, there was 12.3° ± 8.3° of internal rotation and 10.7° ± 3.8° of eversion. The authors noted that knowledge of ankle kinematics of joints with OA may help in the assessment of the results of treatment interventions and in the design of prostheses.